A power supply with a capacitor providing an output voltage. A switch is connected between a voltage source and the capacitor. A control terminal of the switch has a switching threshold. The switch conducts a charging current from the voltage source into the capacitor. A control circuit controls the switch on when the voltage source is below a predetermined level and off when the voltage source is above the level. A control voltage supply circuit provides a control supply voltage. A control terminal voltage for the switch derived from the control supply voltage with a magnitude in excess of the switching threshold drives the switch on in a saturated region of operation.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A power supply circuit comprising: a charge storage capacitor having a first capacitor terminal adapted to provide a power supply voltage of the power supply and a second capacitor terminal coupled to a circuit common; a first switching device having a first switching terminal adapted to be connected to a voltage source, a second switching terminal operatively coupled to the first capacitor terminal of the charge storage capacitor, and a control terminal, the first switching device characterized by a control terminal switching threshold voltage, the first switching device adapted to conduct a charging current from the first switching terminal to the second switching terminal and into the charge storage capacitor; a control circuit controlling an on/off operation of the first switching device whereby the first switching device is operable to turn on when the magnitude of the voltage of the voltage source is below a predetermined level and turn off when the magnitude of the voltage of the voltage source is above the predetermined level; and a control voltage supply circuit operatively coupled between the first switching terminal of the first switching device and the first capacitor terminal of the charge storage capacitor, the control voltage supply circuit providing a control supply voltage; wherein a control terminal voltage derived from the control supply voltage is provided to the control terminal of the first switching device when the control circuit controls the first switching device to be on, the control terminal voltage having a magnitude in excess of the switching threshold voltage, thereby driving the switching device on in a saturated region of operation.
2. The power supply circuit of claim 1 , wherein the control circuit comprises a second switching device controlled by the voltage source whereby when the voltage of the voltage source exceeds the predetermined level, the second switching device shunts current away from the control terminal of the first switching device, turning the first switching device off.
3. The power supply circuit of claim 1 , further comprising a latching switch coupled to the second switching device to latch the second switching device on to shunt current away from the control terminal of the first switching device to maintain the second switching device on and thereby keep the first switching device off.
4. The power supply circuit of claim 1 , further comprising a charge storage capacitor voltage regulation circuit for maintaining a voltage across the charge storage capacitor below a preset level.
5. The power supply circuit of claim 4 , wherein the charge storage capacitor voltage regulation circuit turns on said second switching device to shunt current away from the control terminal of the first switching device if the voltage across the charge storage capacitor exceeds the preset level.
6. The power supply circuit of claim 1 , further comprising an overcurrent protection circuit coupled to said first switching device to limit the charging current through the first switching device into the charge storage capacitor.
7. The power supply circuit of claim 6 , wherein the overcurrent protection circuit comprises a third switching device that turns on to shunt current away from said control terminal when the charging current through the first switching device exceeds a preset current level.
8. The power supply circuit of claim 1 , further comprising a voltage regulator coupled to the charge storage capacitor and providing an output voltage of the power supply.
9. The power supply circuit of claim 1 , wherein the control voltage supply circuit comprises an RC network comprising a supply resistor and a supply capacitor, a voltage developed across the supply capacitor being coupled to the control terminal of the first switching device to drive the first switching device into the saturated region of operation.
10. The power supply circuit of claim 9 , wherein the control voltage supply circuit further comprises an avalanche device coupled across the supply capacitor to limit the magnitude of the control supply voltage developed across the supply capacitor.
11. The power supply circuit of claim 10 , wherein the supply capacitor is coupled between the voltage source and said charge storage capacitor.
12. The power supply circuit of claim 1 , further comprising an avalanche device coupled to the control terminal of said first switching device to limit the magnitude of the control terminal voltage applied to the control terminal.
13. The power supply circuit of claim 1 , wherein the first switching device comprises a FET.
14. The power supply circuit of claim 9 , wherein the control voltage supply circuit further comprises a diode in series with the capacitor to prevent discharge of said supply capacitor of said control voltage supply circuit to said voltage source.
15. The power supply circuit of claim 1 , further comprising a diode coupled in series with said charge storage capacitor to prevent discharge of said charge storage capacitor when said first switching device is off.
16. The power supply circuit of claim 2 , wherein the second switching device has a control terminal coupled to a resistor divider circuit, the resistor divider circuit being coupled between the voltage source and circuit common of the power supply circuit.
17. A catear power supply circuit comprising: a charge storage capacitor having a first capacitor terminal adapted to provide a power supply voltage of the power supply and a second capacitor terminal coupled to a circuit common; a first switching transistor having a first switching terminal adapted to be connected to a voltage source, a second switching terminal operatively coupled to the first capacitor terminal of the charge storage capacitor, and a control terminal, the first switching transistor characterized by a control terminal switching threshold voltage, the first switching transistor adapted to conduct a charging current from the first switching terminal to the second switching terminal and into the charge storage capacitor; a control circuit controlling an on/off operation of the first switching transistor whereby the first switching transistor is enabled to be turned on when the magnitude of the voltage of the voltage source is below a predetermined level and to be turned off when the magnitude of the voltage of the voltage source is above the predetermined level; and a control voltage supply circuit operatively coupled between the first switching terminal of the first switching device and the first capacitor terminal of the charge storage capacitor, the control voltage supply circuit providing a control supply voltage; wherein a control terminal voltage derived from the control supply voltage is provided to the control terminal of the first switching device when the control circuit controls the first switching device to be on, the control terminal voltage having a magnitude in excess of the switching threshold voltage, thereby driving the first switching transistor on in a saturated region of operation, the control terminal voltage not supplied to the control terminal when the control circuit controls the first switching transistor to be off.
18. The catear power supply circuit of claim 17 , wherein the control circuit comprises a second switching transistor controlled by the voltage source whereby when the voltage source level exceeds the predetermined level, the second switching transistor shunts current away from the control terminal of the first switching transistor, turning the first switching transistor off.
19. The catear power supply circuit of claim 17 , further comprising a latching transistor coupled to the second switching transistor to latch the second switching transistor on to shunt current away from the control terminal of the first switching transistor to maintain the second switching transistor on and thereby keep the first switching transistor off.
20. The catear power supply circuit of claim 17 , further comprising a charge storage capacitor voltage regulation circuit for maintaining a voltage across the charge storage capacitor below a preset level.
21. The catear power supply circuit of claim 20 , wherein the charge storage capacitor voltage regulation circuit turns on said second switching transistor to shunt current away from the control terminal of the first switching transistor if the voltage across the charge storage capacitor exceeds the preset level.
22. The catear power supply circuit of claim 17 , further comprising an overcurrent protection circuit coupled to said first switching transistor to limit the charging current through the first switching transistor into the charge storage capacitor.
23. The catear power supply circuit of claim 22 , wherein the overcurrent protection circuit comprises a third switching transistor that turns on to shunt current away from said control terminal when the charging current through the first switching transistor exceeds a preset current level.
24. The catear power supply circuit of claim 17 , further comprising a voltage regulator coupled to the charge storage capacitor providing an output voltage of the power supply.
25. The catear power supply circuit of claim 17 , wherein the control voltage supply circuit comprises an RC network comprising a supply resistor and a supply capacitor, a voltage developed across the supply capacitor being coupled to the control terminal of the first switching transistor to drive the first switching transistor into the saturated region of operation.
26. The catear power supply circuit of claim 25 , wherein the control voltage supply circuit further comprises an avalanche device coupled across the supply capacitor to limit the magnitude of the control supply voltage developed across the supply capacitor.
27. The catear power supply circuit of claim 26 , wherein the supply capacitor is coupled between the voltage source and said charge storage capacitor.
28. The catear power supply circuit of claim 17 , further comprising an avalanche device coupled to the control terminal of said first switching transistor to limit the magnitude of the control terminal voltage applied to the control terminal.
29. The catear power supply circuit of claim 17 , wherein the first switching transistor comprises a FET.
30. The catear power supply circuit of claim 25 , wherein the control voltage supply circuit further comprises a diode in series with the supply capacitor to prevent discharge of said supply capacitor of said control voltage supply circuit to said voltage source.
31. The catear power supply circuit of claim 17 , further comprising a diode coupled in series with said charge storage capacitor to prevent discharge of said charge storage capacitor when said first switching transistor is off.
32. The catear power supply circuit of claim 18 , wherein the second switching transistor has a control terminal coupled to a resistor divider circuit, the resistor divider circuit being coupled between the voltage source and circuit common of the power supply circuit.
33. A lighting dimmer for controlling the power delivered from a voltage source to a lamp load, the dimmer comprising: an electronic lamp dimmer circuit controlling the power delivered to the lamp load; a catear power supply coupled to the electronic lamp dimmer circuit for providing power to electronic circuits of the lighting dimmer, the catear power supply circuit comprising: a charge storage capacitor having a first capacitor terminal adapted to provide and output voltage of the power supply and a second capacitor terminal coupled to a circuit common; a switching device having a first switching terminal adapted to be connected to the voltage source, a second switching terminal operatively coupled to the first capacitor terminal of the charge storage capacitor, and a control terminal, the first switching device characterized by a control terminal switching threshold, the switching device adapted to conduct a charging current from the first switching terminal to the second switching terminal and into the charge storage capacitor; a control circuit controlling the on/off operation of the switching device whereby the switching device is operable to turn on when the magnitude of the voltage of the voltage source is below a predetermined level and turn off when the magnitude of the voltage of the voltage source is above the predetermined level; and a control voltage supply circuit operatively coupled between the first switching terminal of the first switching device and the first capacitor terminal of the charge storage capacitor, the control voltage supply circuit providing a control supply voltage; wherein a control terminal voltage derived from the control supply voltage is provided to the control terminal of the switching device when the control circuit controls the first switching device to be on, the control terminal voltage having a magnitude in excess of the switching threshold voltage thereby driving the switching device on in a saturated region of operation.
34. The lighting dimmer of claim 33 , wherein the lamp dimmer circuit includes a triac.
35. The lighting dimmer of claim 33 , wherein the electronic circuits include at least one of a microprocessor and a display.
36. The lighting dimmer of claim 33 , wherein the electronic circuits include an RF circuit.
37. The lighting dimmer of claim 33 , wherein the electronic circuits include the electronic lamp dimmer circuit.
38. A method of generating a power supply voltage in a two wire dimmer having a phase cut switching device adapted to be coupled between a hot side of an AC line and a lamp load for providing power to the lamp load, the method comprising the steps of: receiving an AC waveform from the hot side of the AC line; charging a charge storage capacitor from the AC line through a charge storage switching device during regions of the AC waveform when the phase cut switching device is off to generate the power supply voltage across the charge storage capacitor; generating a control supply voltage across a supply capacitor, the control supply voltage referenced to the power supply voltage; deriving a control terminal voltage from the control supply voltage, the control terminal voltage having a magnitude in excess of a control terminal threshold voltage of the switching device; providing the control terminal voltage to a control electrode of the charge storage switching device to drive the charge storage switching device on in a saturated region of operation when a magnitude of the AC waveform is less than a predetermined level; turning the charge storage switching device off when the AC waveform is above the predetermined level; and providing the power supply voltage across the charge storage capacitor as an output voltage.
39. The method of claim 1 , wherein the step of generating a control supply voltage across a supply capacitor comprises rectifying the AC waveform to produce a rectified voltage, providing the rectified voltage to charge the supply capacitor, and limiting the control supply voltage across the supply capacitor.
40. The method of claim 38 , wherein the control terminal voltage has a magnitude of 15 volts.
41. The method of claim 38 , further comprising regulating the output voltage across the charge storage capacitor.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
October 22, 2008
May 31, 2011
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